We hypothesise that viral infection could play an etiologic role in biliary atresia (BA), one of the most serious digestive/liver diseases of infancy. However, to date attempts to isolate or discover viruses in patients with BA have been limited to small numbers of patients, have yielded conflicting results, and the methodology has been limited to serological, and/or tissue analysis looking for known viruses. The Biliary Atresia Research Consortium's (BARC) tissue repository offers the opportunity for systematic search for the long-suspected viral etiology of this disease and this BARC Ancillary Study proposes to apply a powerful and novel method of viral discovery, using a DNA microarray harboring the most highly conserved 70mer oligonucleotide sequences from every fully sequenced viral genome in GenBank. Strategic targeting of the conserved regions of viral genomes enables not only massively parallel analysis of essentially all known viruses, but also maximizes the probability of detecting unknown viruses. Identification of a viral etiology should serve as the launching point for additional studies focused on disease mechanisms, treatment and prevention. This proposal aims to apply this powerful and novel methodology to the investigation of a possible viral etiology of BA, by examining liver and bile duct remnants from EHBA patientsenrolled in the BARC with the `acquired'or `perinatal'phenotype. A small number of tissues will be examined from patients with the `embryonal'phenotype, and from patients with known non-viral liver diseases eg alpha-1-antitrypsin deficiency, allagille syndrome etc. as control tissue. Dr Wang's laboratory at Washington University St Louis has been at the forefront of new viral discovery. For example, during the recent SARS outbreak, hybridization patterns observed using the pan-viral microarray helped identify SARS as a novel coronavirus, demonstrating the power and utility of this approach.